In the description that follows reference is made to certain structures and methods, however, such references should not necessarily be construed as an admission that these structures and methods qualify as prior art under the applicable statutory provisions. Applicants reserve the right to demonstrate that any of the referenced subject matter does not constitute prior art.
In the field of conductor (metal) processing, plasma processing chambers are commonly used to etch one or more layers formed on a substrate. During etching, the substrate is supported on a substrate support surface within the chamber. Substrate supports can include edge rings positioned around the substrate support (i.e., around the substrate) for confining plasma to the volume above the substrate and/or to protect the substrate support, which typically includes a clamping mechanism, from erosion by the plasma. The edge rings, sometimes called focus rings, can be sacrificial (i.e., consumable) parts. Conductive and non-conductive edge rings are described in commonly-owned U.S. Pat. Nos. 5,805,408; 5,998,932; 6,013,984; 6,039,836 and 6,383,931.
During plasma etching, plasma is formed above the surface of a substrate by adding large amounts of energy to a gas (or gas mixture) at low pressure. The plasma may contain ions, free radicals, and neutral species with high kinetic energies. By adjusting the electrical potential of the substrate, charged species in the plasma can be directed to impinge upon the surface of the substrate and thereby remove material (e.g., atoms) therefrom.